This invention relates to a process of incinerating waste materials, in which the waste materials are reduced in size as far as necessary and are subsequently optionally mixed with fuel and are incinerated at temperatures from 1000.degree. to 1700.degree. C. to form liquid ash, a major part of which is removed as liquid slag from the combustion chamber and the pollutants are removed from the exhaust gases produced by the incineration.
Waste materials--i.e., household and industrial wastes, hazardous wastes, agricultural waste products and clarifier sludge--have been incinerated on a large scale for many years in order to destroy pollutants contained in the waste material and to considerably decrease the amount of waste material which is to be dumped. In the past, the incineration of waste material has often given rise to problems because the exhaust gases as well as the ashes and fly dusts which are formed contain toxic substances, which pollute the environment and must be removed from the exhaust gases, ashes and fly dusts by expensive processes. As an example, attention may be directed here to the dioxins, which are formed by the incineration of waste materials and the formation of which must substantially be suppressed by an appropriate processing or which must be removed from purifying processes from the products of the incineration of waste materials. Specifically, the fly dusts, which are formed by the incineration of waste materials and consist of very fine ash particles, constitute a considerable hazard in the environment because they contain highly toxic organic compounds--i.e. dioxins, halogenated furans and highly condensed aromatic hydrocarbons--as well as heavy metals and heavy metal compounds and the latter will be dissolved at least in part in contact with water and in that case will contaminate the surface water and ground water. Because the plants for the incineration of waste materials contain considerable amounts of pollutants, they must be handled as hazardous wastes.
Numerous attempts have been made to eliminate the potential hazards which are due to the solid residues formed by the incineration of waste materials and are particularly due to the fly dusts. But it has been found again and again that the previously employed processes of incinerating waste materials result in solid residues which necessarily contain pollutants in considerable amounts. For instance, Published European Patent Application 305,779 discloses for the disposal of waste materials by incineration a process in which the dried waste materials are incinerated in a cyclone at temperatures above 1500.degree. C. to form a molten slag having a low pollutant content and a hot exhaust gas. The liquid slag flows form a furnace which succeeds the incinerating cyclone. The exhaust gas is subjected to a first exhaust gas cooling and the valuable materials are then removed by a partial condensation, whereafter the exhaust gas is cooled further and the pollutants are subsequently removed by a partial condensation at a lower temperature. Because droplets of liquid ash are suspended in the exhaust gas, the partial condensation results in a formation of fly dust, which contains pollutants, or the partial condensation involves in a collection of valuable materials, which undesirably cannot be utilized because they have a high content of fly dust so that they must also be handled as pollutant-containing solid residues.